1. Field
Electronic device packages and the manufacture thereof.
2. Background
Integrated circuit (IC) chips or die are typically assembled into a package that is soldered to a printed circuit board (PCB). A chip or die may have contacts on one surface (e.g., such as a field or array of contacts) that are electrically connected to a first set of contacts on one surface of an electronic device package (e.g., such as a chip or die package), and there may be another set of contacts on the package for connection to a PCB, such as a mother board. Thus, a circuit device, such as a chip or a die can be assembled into a package on a substrate, strip, or wafer having multiple packages. Once the packages are assembled, each package may be separated from the other packages and subsequently attached to a PCB. Electronic access to and operation of circuit devices, such as circuit devices on a semiconductor (e.g., silicon) substrate, may be provided by one set of solder balls and/or contact wires between the circuit device and a circuit device package, and a second set of solder balls between the package and contacts of another electronic device (e.g., such as a PCB).
During manufacture and assembly, such a package may experience thermal variation and vertical tensile strain. In addition, the package may include materials having various coefficients of thermal expansion (CTE). For example, multiple packages may be formed or mounted on a substrate, strip, or wafer by mounting a circuit device at each of the package locations, filling the space between the circuit device and the location with an underfill material, and then coating the circuit device and location with a mold material. Subsequently, each package location including the circuit device mounted therein, may be singulated or separated from the other packages and to form a single package for attaching to a PCB or mother board. Therefore, there may be CTE mismatches between a substrate on which packages are manufactured (e.g., such as a substrate on which multiple circuit devices are assembled to multiple package locations, underfilled, and molded), the circuit devices themselves, the underfill material (e.g., material to fill the gap between the circuit devices and the substrate), and the mold material (e.g., such as material to seal out moisture, formed over the circuit devices, package locations, and fill material). Thus, a substrate having a number of packages formed thereon at package locations may experience warping or bowing depending on the degree of CTE mismatches between the materials mentioned above, the thicknesses of the materials, the number of packages formed on the substrate, the space between the packages, and the number and intensity of thermal variations experienced during manufacture of the packages and assembly of the circuit devices to the packages. This warping may cause delamination or bowing of layers of the package and of the circuit devices assembled into the packages.
Moreover, after formation of the packages (e.g., formation of the packages to include the circuit devices at each package location), it may be difficult to singulate or separate the packages from one another without damaging the packages or circuit devices in the packages because of the warping or bowing of the multi-package substrate due to CTE mismatches and thermal variations as described above. For example, during singulation, the force used to compress or flatten a warped substrate having multiple packages, prior to separating the packages, may damage the packages or circuit devices in the package. Therefore, it is generally desirable to manufacture a substrate of multiple packages having reduced warpage or bowing prior to, during, and after assembling circuit devices into the packages.